Organic light emitting display device and method for fabricating the same

ABSTRACT

The present application relates to a method for fabricating an organic light emitting display device, comprising: forming a drive thin film transistor on a substrate at a non-light emission region; forming a protective layer on the substrate; forming a color filter on the protective layer; forming a planarizing layer on a protective layer including the color filter; selectively removing the protective layer and the light compensating layer to form a first drain contact hole which exposes a drain electrode of the drive thin film transistor; forming a light compensating layer on the planarizing layer to have a second drain contact hole which exposes the first contact hole, and a dummy hole to expose the planarizing layer; and forming an organic light emitting element on the light compensating layer to be in contact with the drain electrode through the first and second drain contact holes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of co-pending application Ser. No.13/626,609 filed on Sep. 25, 2012, which claims priority to KoreanPatent Application No. 10-2011-0099986, filed on Sep. 30, 2011, theentire contents of all of the above applications are hereby incorporatedby reference.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present invention relates to organic light emitting display devices,and more particularly to an organic light emitting display device whichcan prevent a light compensation layer from cracking; and a method forfabricating the same.

2. Discussion of the Related Art

An image display device which realizes various pieces of information isa core technology of an information and communication times anddeveloping in a direction of high performance while thinner, lighter,and portable. Recently, as a bendable flexible display is in demandowing to pursuance of spatial convenience, the organic light emittingdisplay device is spot lighted, in which a light emitting quantity of anorganic light emitting layer thereof is controlled by a flat displaydevice.

The organic light emitting display device has a thin film transistorarray on a substrate, an organic light emitting display element on thethin film transistor array, and a glass cap for isolating the organiclight emitting display device from an external environment. The organiclight emitting display device uses electroluminescence in which a lightis emitted by coupling energy of an electron and a hole. If an electricfield is applied to a cathode and an anode formed on both ends of anorganic light emitting layer, the electron and the hole are injected andtransmitted to the organic light emitting layer, and the electron andthe hole which form a pair in the organic light emitting layer dropsfrom an excited state to a base state to emit the light.

In detail, the organic light emitting display device is provided withsub-pixels disposed at every region defined as gate lines GL and datalines DL cross. Each of the sub-pixels receives a data signal suppliedthrough the data line DL whenever a gate pulse is supplied to the gateline GL to emit the light corresponding to the data signal.

FIG. 1 illustrates a circuit diagram of a related art organic lightemitting display device, and FIG. 2 illustrates a photograph of a lightcompensating layer having a crack taken place therein.

Referring to FIG. 1, each of the sub-pixels has an organic lightemitting element EL having a cathode connected to a ground voltagesource GND, and a cell drive unit 152 connected to a gate line GL, adata line DL, and a supply voltage source VDD as well as an anode of theorganic light emitting element EL for driving the organic light emittingelement EL. The cell drive unit 152 has a switching thin film transistorT1, a drive thin film transistor T2, and a capacitor C.

The switching thin film transistor T1 is turned on when a scan pulse issupplied to the gate line GL to supply a data signal supplied to a dataline DL to a first node N1. The data signal supplied to the first nodeN1 is charged to the capacitor C, and supplied to a gate terminal of thedrive thin film transistor T2. The drive thin film transistor T2controls a current being supplied to the organic light emitting elementEL from the supply voltage source VDD in response to the data signalsupplied to the gate terminal to control a light emitting quantity ofthe organic light emitting element EL.

And, since the capacitor C discharges the data signal even if theswitching thin film transistor T1 is turned off, the drive thin filmtransistor T2 supplies the current from the supply voltage source VDD tothe organic light emitting element EL to sustain the light emission fromthe organic light emitting element EL until a next frame data signal issupplied.

The drive thin film transistor has an active layer with a source region,a channel region, and a drain region, a gate electrode overlapped withthe channel region of the active layer with a gate insulating filmdisposed therebetween, a source electrode connected to the source regioninsulated from the gate electrode with an interlayer insulating filmdisposed therebetween, and a drain electrode connected to the drainregion. There are a protective layer formed on the interlayer insulatingfilm including the source and drain electrodes, and a color filterformed on the protective layer. There are a planarizing layer formed onthe protective layer including the color filter, and the organic lightemitting element formed on the planarizing layer in contact with thedrain electrode exposed by selective removal of the protective layer andthe planarizing layer.

In the meantime, if the organic light emitting display device is a whiteorganic light emitting display device which emits a white light, sincethe white color is produced by mixing red, green and blue R, G, B colorfilters, light emitting quantities of the red color, the green color andthe blue color R, G, B vary depending upon an angle of view, causingcolor shift to drop a display quality.

Consequently, in order to prevent the color shift from taking place, thewhite organic light emitting display device has a light compensatinglayer formed of an inorganic material on the planarizing layer. However,stress is generated at a boundary of the light compensating layer andthe planarizing layer due to a difference of thermal expansivecoefficients between the light compensating layer and the planarizinglayer to cause a crack at the light compensating layer, as shown in FIG.2. In this case, an anode formed on the light compensating layer isbroken, dropping reliability of the organic light emitting displaydevice.

SUMMARY OF THE DISCLOSURE

Accordingly, the present invention is directed to an organic lightemitting display device, and a method for fabricating the same.

An object of the present invention is to provide an organic lightemitting display device in which a dummy hole is formed in a lightcompensating layer to moderate stress at a boundary of the lightcompensating layer and the planarizing layer; and a method forfabricating the same.

Additional advantages, objects, and features of the disclosure will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, anorganic light emitting display device includes a plurality of sub-pixelsformed on a substrate, wherein each sub-pixel having a light emissionregion and a non light emission region includes; a drive thin filmtransistor on the substrate at the non light emission region, aprotective layer on the substrate including the drive thin filmtransistor, a color filter on the protective layer at the emissionregion, a planarizing layer on the protective layer including the colorfilter, a first drain contact hole in the protective layer and theplanarizing layer to expose a drain electrode of the drive thin filmtransistor, a light compensating layer on the planarizing layer, thelight compensating layer having a second drain contact hole whichexposes the first drain contact hole and one or a plurality of dummyholes which expose the planarizing layer, and an organic light emittingelement on the light compensating layer to be in contact with the drainelectrode through the first and second drain contact holes and includinga first electrode, an organic light emitting layer, and a secondelectrode.

The dummy holes have a total area the same with an area of the drainsecond contact hole.

The light compensating layer is an inorganic film of a silicon groupmaterial, such as SiNx and SiO₂.

In another aspect of the present invention, a method for fabricating anorganic light emitting display device having a plurality of sub-pixels,each having a light emission region and a non-light emission region,comprising the steps of: forming a drive thin film transistor on asubstrate at non-light emission region; forming a protective layer onthe substrate including the drive thin film transistor; forming a colorfilter on the protective layer; forming a planarizing layer on theprotective layer including the color filter; selectively removing theprotective layer and the light compensating layer to form a first draincontact hole which exposes a drain electrode of the drive thin filmtransistor; forming a light compensating layer on the planarizing layerto have a second drain contact hole which exposes the first contacthole, and at least one dummy hole to expose the planarizing layer; andforming an organic light emitting element on the light compensatinglayer to be in contact with the drain electrode through the first andsecond drain contact holes.

The second drain contact hole and the at least one dummy hole are formedby dry etching.

The dummy hole has a total area the same with an area of the seconddrain contact hole.

The light compensating layer is an inorganic film of a silicon groupmaterial, such as SiNx and SiO₂.

Thus, the organic light emitting display device, and the method forfabricating the same of the present invention minimizes the stresstransmitted to the light compensating layer by moderating thermalexpansive force of the planarizing layer with the dummy hole in thelight compensating layer which is formed on the planarizing layer 190for preventing color shift from taking place. Eventually, the lightcompensating layer is prevented from cracking, thereby improvingreliability of the organic light emitting display device.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide fartherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the disclosure andtogether with the description serve to explain the principle of thedisclosure. In the drawings:

FIG. 1 illustrates a circuit diagram of a related art organic lightemitting display device.

FIG. 2 illustrates a photograph of a light compensating layer having acrack taken place therein.

FIG. 3A illustrates a plan view of an organic light emitting displaydevice in accordance with a preferred embodiment of the presentinvention.

FIG. 3B illustrates a section across a line I-I′ in FIG. 3A.

FIG. 4 illustrates a plan view of an organic light emitting displaydevice in accordance with another preferred embodiment of the presentinvention.

FIGS. 5A to 5G illustrate sections showing the steps of a method forfabricating an organic light emitting display device in accordance witha preferred embodiment of the present invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Reference will now be made in detail to the specific embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

The organic light emitting display device of the present invention whichis a white organic light emitting display device may produce the whitecolor only with red, green, and blue sub-pixels, or, in order to obtaina high white color luminance, a white color sub-pixel which produces thewhite color may be added to the red, green, and blue sub-pixels to formone pixel of the red, green, blue, and white sub-pixels.

An organic light emitting display device, and a method for fabricatingthe same of the present invention will be described with reference tothe attached drawings, in detail.

FIG. 3A illustrates a plan view of an organic light emitting displaydevice in accordance with a preferred embodiment of the presentinvention, FIG. 3B illustrates a section across a line I-I′ in FIG. 3A,and FIG. 4 illustrates a plan view of an organic light emitting displaydevice in accordance with another preferred embodiment of the presentinvention.

Referring to FIG. 3A, the organic light emitting display device of thepresent invention has a plurality of red R, green G, blue B, and white Wsub-pixels formed on a substrate 100 to form one pixel of the red R,green G, blue B, and white W sub-pixels. An arrangement of the red R,green G, blue B, and white W sub-pixels is not limited to an arrangementshown in the drawing.

Each of the red R, green G, blue B, and white W sub-pixels includes adrive thin film transistor formed on the substrate 100 and an organiclight emitting element connected to the drive thin film transistor. Thedrive thin film transistor has an active layer 120, a gate electrode 140and source and drain electrodes 160 a and 160 b.

At first, as shown in FIG. 3B, a buffer layer 110 is formed on thesubstrate 100, and the active layer 120 having a source region 120 a, adrain region 120 c and a channel region between the source and drainregions 120 a and 120 c is formed on the buffer layer 110. A gateinsulating film 130 is formed on the substrate including the activelayer 120. Then, the gate electrode 140 is formed on the gate insulatingfilm 130 to overlap with the channel region 120 c of the active region120.

An interlayer insulating film 150 is formed on the gate insulating film130 including the gate electrode 140. The source electrode 160 a and adrain electrode 160 b insulated from the gate electrode 140 are formedon the interlayer insulating film 150. The source electrode 160 a andthe drain electrode 160 b are in contact with the source region 120 aand the drain region 120 c of the active layer 120 through contact holespassed through the interlayer insulating film 150 and the gateinsulating film 130, respectively.

A protective layer 170 is formed on the interlayer insulating film 150including the source electrode 160 a and the drain electrode 160 b. Theprotective layer 170 is formed of an inorganic insulating material or anorganic insulating material. A color filter 180 is formed on theprotective layer 170 at a light emission region. A planarizing layer ofan organic material is formed on an entire surface of the protectivelayer 170 including the color filter 180. And, by selective removal ofthe protective layer 170 and the planarizing layer 190, a first draincontact hole (Not numbered) is formed, which exposes the drain electrode160 b of the drive thin film transistor.

A light compensating layer 200 is formed on the planarizing layer 190.The light compensating layer 200 is formed of a silicon group inorganicmaterial, such as SiNx, and SiO₂ for preventing color shift from takingplace due to differences of light emission quantities of the red R,green G, and blue B colors depending on an angle of view. Particularly,it is preferable that the light compensating layer 200 is formed of atransparent inorganic film having transmittancy of 50% to 100% so thatthe light from the organic light emitting layer to be described later isemitted through the substrate 100.

The light compensating layer is formed on an entire surface of theplanarizing layer having the first drain contact hole. The lightcompensating layer has a second drain contact hole 200 a by removing aportion of a region corresponding to the first drain contact hole forconnecting the organic light emitting display element formed on thelight compensating layer to the drain electrode 160 b. However, asdescribed before, a difference of thermal expansive coefficients of thelight compensating layer 200 which is an inorganic layer and theplanarizing layer 190 which is an organic layer causes stress at aboundary of the light compensating layer 200 and the planarizing layer190 to cause a crack at the light compensating layer 200.

In general, an inorganic substance has a thermal expansive coefficientdifferent from an organic substance. When the light compensating layer200 is formed on the planarizing layer 190, or a process is progressed,in which a thin film is formed on the light compensating layeradditionally, a heat treatment process is accompanied. However, sincethe planarizing layer 190 has a thermal expansive coefficient higherthan the thermal expansive coefficient of the light compensating layer,the stress is caused at the time of heat treatment due to the differenceof the thermal expansive coefficients, which may cause a defect ofirregular bending or a fine crack at the light compensating layer 200.

And, due to this, an anode 300 formed on the light compensating layer200 breaks, dropping reliability of the organic light emitting displaydevice. Moreover, since the light compensating layer 200 is formed by alow temperature process for preventing damage, such as thermaldecomposition, from taking place at the planarizing layer 190, densityof the light compensating layer is low to increase a probability ofcausing the bending defect or the crack.

Therefore, in order to prevent the crack from taking place at lightcompensating layer 200 by moderating the stress at the planarizing layer190 and the light compensating layer 200, the light compensating layer200 is removed selectively to form one or a plurality of dummy holes 200b which expose the planarizing layer 190. As shown in FIG. 4, if thedummy hole 200 b is one, the dummy hole 200 b may be formed in a barshape.

Eventually, the organic light emitting display device of the presentinvention makes the expansive force of the boundary at which the lightcompensating layer 200 and the planarizing layer 190 are in contact toconcentrate at the dummy hole 200 b when the planarizing layer 190expands thermally following elevation of a temperature of theplanarizing layer 190. And, the dummy hole 200 b moderates the expansiveforce of the planarizing layer 190, minimizing the stress between theplanarizing layer 190 and the light compensating layer 200, whichminimizes the stress to the light compensating layer 200 preventing thecrack from taking place at the light compensating layer 200, at the end.

Especially, the dummy hole 200 b is formed on one side of the colorfilter 180. Since an organic light emitting layer 320 is formed on thecolor filter 180, it is preferable that the dummy hole 200 b is formedat a non-light emission region which does not face the red R, green G,blue B, and white W sub-pixels, for preventing an aperture region frombecoming smaller. The dummy hole 200 b may be singular or plural, and,since the dummy hole 200 b is formed at the same time with the seconddrain contact hole 200 a, it is preferable that a total area of thedummy hole 200 b is the same with an area of the second drain contacthole 200 a to balance etch rates. This is for preventing the planarizinglayer 190 or the drain electrode 160 b from being etched by etch gaswhen an inorganic film formed for forming the light compensating layer200 on the entire surface of the planarizing layer 190 is removedselectively by dry etching for forming the dummy hole 200 b and thesecond drain contact hole 200 a. If the area of the dummy hole 200 b isdifferent from the area of the second drain contact hole 200 a, theplanarizing layer 190 or the drain electrode 160 b can be etched by etchgas. Particularly, if the drain electrode 160 b is etched, defectivecontact of a first electrode 300 and the drain electrode 160 b may takeplace.

The first electrode 300 is formed on the light compensating layer 200 tobe in contact with the drain electrode 160 b through the first andsecond drain contact holes 190 a and 200 a. A bank 400 having bank holesis formed on the light compensating layer 200 including the firstelectrode 300 for defining a light emission region. The bank hole of thebank 400 exposes the first electrode 300 at the light emission region.

Then, the organic light emitting display element is formed on the firstelectrode 300. The organic light emitting display element includes thefirst electrode 300, a Hole injection layer (HIL)(Not shown), a Holetransport layer (HTL) 310, an organic light emitting layer 320, anelectron transport layer (ETL) 330, an electron injection layer (EIL)(Not shown), and a second electrode 340.

In detail, the first electrode 300 is formed on the light compensatinglayer 200 to be connected to the drain electrode 160 through the firstand second drain contact holes 200 a. The first electrode 300, being ananode, is formed of a transparent conductive material, such as ITO(Indium Tin Oxide) and IZO (Indium Zinc Oxide). According to this, thelight emits from the organic light emitting layer 320 to the substrate100 through the first electrode 300.

The hole injection layer (Not shown) and the hole transport layer 310are formed on the first electrode 300 in the bank hole in succession.The organic light omitting layer 320 is formed on the hole transportlayer 310, and the electron transport layer 330, the electron injectionlayer (Not shown), and the second electrode 340 are formed on theorganic light emitting layer 320. The second electrode 340, being acathode, is formed of a reflective metal such as aluminum Al forreflecting the light front the organic light emitting layer 320 towardthe first electrode 300.

The organic light emitting display device produces an exciton if avoltage is applied between the first electrode 300 and the secondelectrode 340 as the hole injected from the first electrode 300 toorganic light emitting layer 320 and the electron injected from thesecond electrode 340 to the organic light emitting layer 320 re-couplein the organic light emitting layer 320. And, as the exciton drops to aground state, the light emits, and as the light passes through the colorfilter under the organic light emitting display device, a light of acolor corresponding to the color filter 180 is emitted.

FIGS. 5A to 5G illustrate sections showing the steps of a method forfabricating an organic light emitting display device in accordance witha preferred embodiment of the present invention.

Referring to FIG. 5A, a buffer layer 110 is formed on a substrate 100,and a drive thin film transistor including an active layer 120, a gateelectrode 140, a source electrode 160 a, and a drain electrode 160 b isformed on the buffer layer 110. The drive thin film transistor is formedby a following method.

After Amorphous silicon is deposited on the buffer layer 110, theamorphous silicon is crystallized into polycrystalline silicon by laserbeam or heat treatment. The polycrystalline silicon is patterned byphotolithography and etching to form an active layer 120. A gateinsulating film 130 is formed on an entire surface of the buffer layer110 including the active layer 120, and a gate electrode 140 is formedon the gate insulating film 130.

And, n⁺ impurities are injected to both sides of the active layer 120 byusing the gate electrode 140 as a mask, to form a source region 120 aand a drain region 120 c opposite to each other with a channel region120 b of the active region 120 disposed therebetween. An interlayerinsulating film 150 is formed on the gate insulating film 130 having thegate electrode 140 formed thereon, and the interlayer insulating film150 and the gate insulating film 130 are removed selectively, to formfirst and second contact holes which expose the source region 120 a andthe drain region 120 c at the active layer 120.

A source/drain metal layer (Not shown) is formed on the interlayerinsulating film 150 having the first and second contact holes (Notnumbered) formed therein, and patterned, to form the source electrode160 a and the drain electrode 160 b. In this instance, the sourceelectrode 160 a is in contact with the source region 120 a through thefirst contact hole and the drain electrode 160 b is in contact with thedrain region 120 c through the second contact hole.

Then, referring to FIG. 5B, a protective layer 170 of organic insulatingmaterial or inorganic insulating material is formed on an entire surfaceof the interlayer insulating film 160 including the source electrode 160a and the drain electrode 160 b. A color filter 180 is formed on theprotective layer 170, and selectively removed to remain at a lightemission region. Then, as shown in FIG. 5C, a planarizing layer 190 isformed on an entire surface of the protective layer 170 including thecolor filter 180, and the protective layer 170 and the planarizing layer190 are removed selectively, to form a first drain contact hole 190 awhich exposes the drain electrode 160 b.

Then, referring to FIG. 5D, an inorganic film (Not shown) of a silicongroup, such as SiNx and SiO₂, is deposited on an entire surface of theplanarizing layer 190. It is preferable that the inorganic film is atransparent inorganic film having transmittancy of 50% to 100% so thatthe light from an organic light emitting layer to be described later isemitted through the substrate 100. Then, the inorganic film is removedselectively by photolithography and etching to form a light compensatinglayer 200.

The light compensating layer 200 includes a second drain contact hole200 a which exposes the drain electrode 160 b as a region correspondingto the first drain contact hole 190 a, and, at the same time with this,one or a plurality of dummy holes 200 b which expose the planarizinglayer 190 on one side of the color filter 180. The dummy hole 200 b isformed for preventing the light compensating layer from cracking due tostress at a boundary of the light compensating layer 200 and theplanarizing layer 190 caused by a difference of thermal expansivecoefficients between the light compensating layer 200 of the inorganicfilm and the planarizing layer 190 of the organic film.

In general, an inorganic substance has a thermal expansive coefficientdifferent from an organic substance. When the light compensating layer200 is formed on the planarizing layer 190, or a process is progressed,in which a thin film is formed on the light compensating layeradditionally, a heat treatment process is accompanied. However, sincethe planarizing layer 190 has a thermal expansive coefficient higherthan the thermal expansive coefficient of the light compensating layer,the stress is caused at the time of the heat treatment due to thedifference of the thermal expansive coefficients which may cause adefect of irregular bending or a fine crack at the light compensatinglayer 200.

Therefore, the present invention suggests forming one or a plurality ofdummy holes 200 b which expose the planarizing layer 190 by removing thelight compensating layer 200 selectively to moderate the stress at theplanarizing layer 190 and the light compensating layer 190 forpreventing the light compensating layer 200 from cracking. According tothis, if the planarizing layer 190 expands thermally as a temperature ofthe planarizing layer 190 is elevated, expansive force of the boundaryat which the light compensating layer 200 and the planarizing layer 190are in contact concentrates on the dummy hole 200 b to moderate theexpansive force of the planarizing layer 190.

Particularly, since the dummy holes 200 b are formed at the same timewith the second drain contact hole 200 a, it is preferable that a totalarea of the dummy holes 200 b is the same with an area of the seconddrain contact hole 200 a to balance etch rates.

Then, referring to FIG. 5E, a first electrode 300 is formed on the lightcompensating layer 200 to be in contact with the drain electrode 160 bthrough the first and second drain contact holes 190 a and 200 a. Thefirst electrode 300 is formed by deposition, such as sputtering. And, asshown in FIG. 5F, a bank 400 is formed on the light compensating layer200 including the first electrode 300. The bank 400 has a bank hole toexpose the first electrode 300 at the light emission region,selectively.

Referring to FIG. 5G, a hole injection layer (Not shown) and a holetransport layer 310 are formed on the first electrode 300 in the bankhole, and an organic light emitting layer 320 is formed on the holetransport layer 310 by a soluble process, such as ink jet, nozzlecoating, spray coating, and roll printing. Then, an electron transportlayer 330, an electron injection layer (Not shown), and a secondelectrode 340 are formed on the organic light emitting layer 320.

According to this, the hole and the electron injected into the organiclight emitting layer 320 re-couple to form an exciton which drops to aground state to emit a light, and as the light passes through the colorfilter 180 under the organic light emitting display element, a light ofa color corresponding to the color filter 180 is emitted.

Thus, the organic light emitting display device, and the method forfabricating the same of the present invention minimizes the stresstransmitted to the light compensating layer by moderating thermalexpansive force of the planarizing layer with the dummy hole in thelight compensating layer which is formed on the planarizing layer 190for preventing color shift from taking place. Eventually, the lightcompensating layer is prevented from cracking, thereby improvingreliability of the organic light emitting display device.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A method for fabricating an organic light emitting display devicehaving a plurality of sub-pixels, each sub-pixel having a light emissionregion and a non-light emission region, the method comprising the stepsof: forming a drive thin film transistor on a substrate at non-lightemission region; forming a protective layer on the substrate includingthe drive thin film transistor; forming a color filter on the protectivelayer; forming a planarizing layer on the protective layer including thecolor filter; selectively removing the protective layer and the lightcompensating layer to form a first drain contact hole which exposes adrain electrode of the drive thin film transistor; forming a lightcompensating layer on the planarizing layer to have a second draincontact hole which exposes the first contact hole, and at least onedummy hole to expose the planarizing layer; and forming an organic lightemitting element on the light compensating layer to be in contact withthe drain electrode through the first and second drain contact holes. 2.The method as claimed in claim 1, wherein the second drain contact holeand the at least one dummy hole are formed by dry etching.
 3. The methodas claimed in claim 1, wherein the at least one dummy hole has a totalarea the same with an area of the second drain contact hole.
 4. Themethod as claimed in claim 1, wherein the light compensating layer is aninorganic film of a silicon group material, such as SiNx and SiO₂. 5.The method as claimed in claim 1, wherein the plurality of sub-pixelshave red, green, blue and white sub-pixels.
 6. The method as claimed inclaim 1, wherein the at least one dummy hole is formed at the non-lightemission region.